Mark Tulin, who has died of a heart attack aged 62, was best known as the bass player of the Electric Prunes, the garage band he formed as a teenager in the San Fernando Valley, Los Angeles, in 1965. He had a varied life outside music, working as a scuba-diving instructor, screenwriter and psychologist whose gentle nature and hippy-era past earned him the nickname "Professor Psychedelic".

Tulin was born in Philadelphia to Jewish parents, Rose and Leon, and later moved to LA. He and his brother, Kip, were encouraged to learn musical instruments. While studying at Taft high school in Woodland Hills, he joined the guitarist Ken Williams, the singer James Lowe and the drummer Michael Weakley in the Sanctions, who became Jim and the Lords, a reference to Joseph Conrad's novel Lord Jim. Like thousands of groups across suburban America, the band could not afford a rehearsal studio, so they practised in their parents' garage. During one rehearsal, they were discovered by Barbara Harris, whose husband, an estate agent, was in the neighbourhood. Harris introduced the band to Dave Hassinger, an engineer at RCA records who became their manager.

Signing to Reprise, the band changed their name to the punchline of a goofy joke ("What's purple and goes buzz-buzz?") and released a single, Ain't It Hard (1966), which flopped. Reprise's parent label, Warner Brothers, were nervous about releasing a follow-up, particularly one with such an odd title, but I Had Too Much to Dream (Last Night) was released with little fanfare in 1966 and became a sleeper hit, rising to No 11 in the US and No 49 in the UK. A follow-up, Get Me to the World On Time, possessed the same elemental energy, but the band's first two albums, The Electric Prunes and Underground (both 1967), lapsed too often into vaudevillian pop inspired by the Beatles' Sgt Pepper's Lonely Hearts Club Band. The group were endorsed by the Vox equipment firm and their songs seemed to use the company's new wah-wah pedals at every opportunity possible.

Mass in F Minor (1968), an attempt to produce a concept album sung in Latin, allowed Tulin to explore a newfound funkiness. The lead track was included on the soundtrack of Easy Rider (1969), but a disastrous live performance of the mass prompted him to leave the band. Tulin briefly attended law school, then played as a studio musician with Cher and Diana Ross. He worked on screenplays, writing the story for Defiance (1980), and studied for a PhD in psychology, later specialising in the treatment of the elderly.

The Electric Prunes re-formed in 2001, touring and recording new material. Tulin was humbled by the interest in his band from later generations of musicians. He contributed to the Smashing Pumpkins' album Teargarden By Kaleidyscope (2009), and played with Billy Corgan and the guitarist Dave Navarro in the band Spirits in the Sky.

Tulin's other great love was scuba-diving. He volunteered regularly at the University of Southern California Catalina Hyperbaric Chamber, a medical facility for the treatment of scuba-diving accidents on Santa Catalina Island, off the California coast. It was while helping out at an underwater cleanup event there that he died. He is survived by his daughter, Samantha, and his wife, Lani, to whom he remained close after their separation.

• Mark Shalom Tulin, musician, born 21 November 1948; died 26 February 2011